Polytetrafluoroethylene (hereinafter referred to briefly as PTFE) is not only resistant to heat and chemicals but is satisfactory in slidability, in particular, with a low coefficient of friction. However, PTFE is generally unsatisfactory in wear resistance and shows a large deformation (creep) under load, particularly at high temperature. Therefore, its utility is seriously restricted in high-temperature, high load applications.
To overcome these drawbacks, various fillers such as glass fiber, glass powder or beads, carbon fiber, graphite, molybdenum disulfide, metallic lubricants, metal oxides, etc. are commonly added to PTFE. Compared with the matrix resins, compositions supplemented with such additives have lower coefficients of friction and, hence, improved wear resistance. Therefore, these resin compositions find application in a broad range of industrial uses such as sliding members, parts and elements, e.g. bearings, gears, bushes, packings, various other sealing members, piston rings, ball valve seats, sliding bands and so on.
Meanwhile, sliding parts are required to have high mechanical strength and low wear characteristics including low counterpart wear characteristics for insuring high energy transmission efficiencies and meeting the maintenance-free requirement. The addition of fillers such as those mentioned above certainly leads to some improvements in the mechanical characteristics and wear resistance of moldings but even the shaped articles obtained by adding carbonaceous fillers, particularly carbon fibers which should promise high mechanical strength and low counterpart wear potentials, are not fully satisfactory in the above-mentioned respects.